Craniosynostosis

Craniosynostosis is a condition where infants are born with an abnormally shaped skull. However, in some cases, a baby may develop craniosynostosis later on. The condition is caused by problems that occur during the development of the skull.

How the skull develops

The skull does not develop as a single section of bone but is made up of five plates of bone. In between each plate there is an opening which is known as a suture. The sutures are designed to give the bone plates flexibility, so that the skull is able to grow along with the brain.

Once the brain and the skull have reached their full, adult size, the sutures fuse together to create a single structure of bone.

In cases of craniosynostosis, one of the sutures fuses before birth, or shortly after. This means that the skull cannot grow in this area, which can lead to overgrowth in another area. This results in an abnormally shaped skull.

How common is craniosynostosis?

Craniosynostosis is a rare type of birth defect that affects an estimated one in every 2,500-3,000 births. Boys are three times more likely to develop craniosynostosis than girls.

Craniosynostosis often develops alone without any other problems. However, in 4.5% of cases, craniosynostosis develops as part of a collection of birth defects known as a syndrome, such as Apert's syndrome or Crouzon's syndrome (both of which are rare genetic conditions).

In most cases of craniosynostosis, the cause is unknown, but researchers believe that it is a genetic condition.

Prognosis

Craniosynostosis does not present an immediate threat or risk to an infant’s health. However, the condition needs to be treated promptly because the resulting abnormal skull development means that if it is not treated, there will not be enough room for the brain to develop as the infant gets older.

If craniosynostosis is left untreated, the bones will begin to squeeze the brain, increasing the pressure on it. This is known as intercranial pressure (ICP). Over time, ICP can cause brain damage.

Surgery is required to treat craniosynostosis. It is usually carried out when an infant is between three to six months of age. Surgery is used to separate the fused bones and ensure that the skull develops normally. It also ensures that the child grows up to have a normal looking face and head.

The causes of craniosynostosis are unknown. From the available evidence, it seems that craniosynostosis is not due to anything that a mother might have done, such as taking certain medications during pregnancy.

Most experts believe that craniosynostosis is caused by mutations (alterations) in certain genes that a baby inherits from their parents. It is thought that the mutated genes may interfere with the normal development of the skull.

Exactly what genes are involved and how they could be passed down through families is still unknown. However, what is known is that if you and your partner have a baby that develops craniosynostosis, there is a small risk that any future child that you conceive together will also develop the condition. This risk is estimated to be between 1-4%.

A paediatrician (a specialist in the treatment of children) will usually be able to diagnose craniosynostosis by carrying out a simple visual examination of the baby’s head.

Any severe distortions of the skull or face will be apparent, and the existence of ridges over fused sutures, or misalignment of the ears, will also provide evidence of craniosynostosis.

In order to confirm a diagnosis of craniosynostosis, an X-ray of the skull may be taken. However, a computerised tomography (CT) scan will provide the best results because it gives a three-dimensional view, showing the sutures in detail.

There are four main types of craniosynostosis which are described below.

Sagittal synostosis

Sagittal synostosis is the most common type of craniosynostosis, accounting for between 50-58% of cases. In sagittal synostosis, the suture at the top of the skull, known as the sagittal suture, fuses. This causes the skull to grow long and narrow, rather than wide.

Coronal craniosynostosis

Coronal craniosynostosis is the second most common type of craniosynostosis, accounting for between 20-29% of cases.

In coronal craniosynostosis, the fusion occurs in one or both of the two sutures that run from the top of the ear, to the top of the skull. These are known as the coronal sutures.

If only one coronal suture is fused, an infant will develop a flattened forehead on the affected side. They may also have a raised eye socket and a crooked nose.

If both coronal sutures are fused, the infant will develop a flat and elevated (prominent) forehead and brow. 

Metopic synostosis

Metopic synostosis occurs in between 4-10% of cases of craniosynostosis. The fusion occurs in the metopic synostosis, which is the suture that runs from the nose to the top of the skull. Infants with metopic synostosis will develop a triangular looking scalp.

Lambdoid synostosis

Lambdoid synostosis is the rarest type of craniosynostosis, occurring in about 2-4% of cases. Fusion takes place in the lambdoid suture, which is a suture that runs along the back of the head. Infants with lambdoid synostosis will develop a flattened head.

Symptoms of intercranial pressure (ICP)

If your child’s craniosynostosis is very mild, it may not be spotted until they begin to experience problems due to an increase in intercranial pressure (ICP) in their skull.

Symptoms of ICP include:

  • vomiting,
  • sluggishness and unresponsiveness,
    irritability,
  • swollen eyes, or the eyes find it difficult to follow a moving object,
  • hearing difficulties, and
  • breathing difficulties.

Craniosynostosis and positional plagiocephaly

Sometimes, parents think that their infant has craniosynostosis when, in fact, they have positional plagiocephaly. Positional plagiocephaly is when the back or side of a baby's head becomes flattened. It is also known as 'flat head syndrome'.

Positional plagiocephaly usually occurs when an infant is encouraged to sleep on their back. Infants should always been encouraged to sleep on their back because this is one of the best ways to prevent sudden infant death syndrome (SIDS).

Positional plagiocephaly is quite a common condition and does not cause any health problems. Although an infant’s head may become flattened during the first few months of life, the shape of their head normally corrects itself by the time the child is one year of age.

It can sometimes be difficult for people who are not health professionals to tell the difference between craniosynostosis and positional plagiocephaly. You should therefore speak to your GP if you are uncertain about whether your child has craniosynostosis or positional plagiocephaly. They should be able to determine whether or not your child has craniosynostosis. 

Surgery

Surgery is the recommended treatment for craniosynostosis.

Surgery is carried out by a neurosurgeon (a specialist in surgery of the nervous system and brain) and a craniofacial surgeon (a specialist in surgery of the face, head, and jaw).

How the operation is performed

During surgery for craniosynostosis, the neurosurgeon will make an incision across the top of your child’s scalp. The neurosurgeon will then remove the affected areas of skull.

The removed bone pieces are reshaped by the craniofacial surgeon before being returned to a normal position within the skull.

The incision is then sealed using dissolvable stitches. This will leave a scar but it will be hidden by hair.

After the operation

Surgery for craniosynostosis is not dangerous, but extra precautions are always taken when surgery involves very young children.

Therefore, following the operation, it is likely that your child will be transferred to an intensive care unit (ICU) for one or two days so that their condition can be carefully monitored. Most children are well enough to leave hospital five days after surgery.

Following surgery, most children will only experience mild pain, but it is common for them to develop swelling around their eyes. The swelling can often prevent them from opening their eyes. While the child may find this annoying or distressing the swelling presents no health risk, and it should go down a few days after the operation.

After having surgery for craniosynostosis, it is likely that your child will be asked to attend regular check-ups so that the future development of their skull can be monitored.